1. Field of the Invention
The present invention relates to flex circuits and more particularly to an assembly which couples a flex circuit between an electronic or optoelectronic device and a rigid structure.
2. Discussion of the Related Art
Electronic devices play an increasingly critical role in the lives of many consumers today. For example, applications as simple as listening to a compact disc player to applications incorporated in life saving machines used in emergency rooms implement electronic devices. Many of these devices read and transfer data using electro-optics.
These devices employ electro optical components capable of reading a medium. These applications may alternatively implement electronic components capable of transmitting and receiving information through a medium. These applications include various components, such as printed circuit boards (PCBs), integrated circuits, passive electrical components, photodetectors, and lasers.
The electronic components associated with these devices must of course electrically interconnect with one another. Among the components which may be used to electrically interconnect the components are flex circuits. Flex circuits typically include a single or multilayer electrically insulating material laminated to or otherwise patterned with metallic conductive pathways, possibly with a protective mask layer covering the multilayer materials to provide electrical isolation. Flex circuits are highly desirable. For example, they are relatively light weight and take-up little space. Flex circuit are also flexible and, because they are flexible, they are easy to install. Furthermore, flex circuits generally exhibit good impedance control, reliability and repeatability, thermal management characteristics, as well as uniform electrical characteristics, which is particularly important in high speed circuitry applications.
FIG. 1 shows a flex circuit 10 connected to a rigid structure in accordance with prior conventional techniques. In this example, the flex circuit 10 connects with a rigid structure such as a PCB 14 by soldering cantilevered leads as shown in related art FIG. 1. As shown, a series of leads 111 associated with the flex circuit 10 are soldered to the PCB 14. However, the soldering joints between the leads 11 and the PCB 14 are stress points where failure may occur. Efforts to reduce the stress at these joints have included applying a bead of adhesive 12 at the soldering joints, thereby providing strain relief as shown in related art FIG. 1. Other efforts to reduce the stress at these joints have included using mechanical fasteners along with or instead of the adhesive. However, the use of typical mechanical fasteners increases space requirements and part count where additional fasteners (i.e. screws) are required. An increase in part count is highly undesirable as it generally translates into reduced reliability and increased cost. Also, the fasteners must be manually positioned and assembled.
In addition, during fabrication of a device which uses the structure shown in FIG. 1, repeated thermal cycling may be required to cure or solder other components of the device. However, various parts, such as the mechanical fasteners and the adhesive, have different thermal properties. Therefore, a stress point where the flex circuit couples with the rigid structure after thermal cycling may be created. Further, the increased amount of parts decreases the reliability. More specifically, the increased part count increases the possibility of failures as there are a greater number of parts that may possibly fail. Vibration, static stresses, and thermal excursions experienced over the life of the assembly may be contributing factors to mechanical failure.
In addition, the adhesive in the assembly shown in related-art FIG. 1 minimizes reworkability of both the flex circuit 10 and the PCB 14. In particular, the use of adhesive makes it difficult to decouple the flex circuit from the rigid structure should a user decide to reuse the component.
Therefore, a need exists for an assembly that couples a flex circuit with a rigid structure in a mechanically robust manner. Furthermore, a need exists to reduce the costs associated with devices using the assembly.